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TINTTTD STATES FREDERICK EISSNER,

PATENT @rrrea OF NElV YORK, N. Y.

THERMOMETER.

SPECIFICATION forming part of Letters Patent No. 320,119, dated June 16, 1885.

Application filed February 11, 1885.

T0 (LZZ whom it may concern.-

Be it known that I, FREDERICK Erssnnu, of the city, county, and State of New York, have invented a new and useful Improvement in Thermometers; and I do hereby deelare that the following is a full and exact de seription thereof, reference being bad to the accompanying drawings, and to the letters of reference marked thereon, making a part of this specification.

My invention relates to an improvement in selfregistering fever-thermometers.

As heretofore constructed these thermometers have been made similar to ordinary thermometers, with the exception that a small index-column is separated by an air-bubble from the upper end of the main column of inercury in the tube. In this simple form the index-column is liable to drop into the tube and be lost. A remedy has been sought for this difficulty by drawing out the end of the mercury-bulb into a slender tube, which is bent up above the bulb in a flat S or loop shaped portion, or by bending the lower end of the graduated mercury-tube above the bulb into a double or S-shaped bend, the bent portion of the tube being protected by an exterior tube or casing.

The object of my invention is to prevent the loss of the index-column without bending the mercury-tube, and to thereby simplify the construction of areliable self-registering thermometer in which the registering device is unalterable. This Ihave accomplished by constructing a thermometer with a sealed mercury-tube eontainin g a column of mercury separated by an air-bubble,and whose lower open end is made to projeetinto an encirelingsealed bulb closely to the bottom of the bulb, whereby saidlower end will remain constantly covered and surrounded by the mercury in the bulb. By this means the air-bubble confined below the upper index-division of the divided column of mercury is absolutely prevented from passing into the bulb, and is positively confined, so that it may not be lost,thus rendering the registering device indestructible so long as the instrument remains intaet,while it permits, also, the construction ofthe thermometer in the straight, slender, cylindrical form of uniform diameter which is most convenient and useful.

(N0 model.)

In the accompanying drawings, Figure 1 is an elevation of my improved registering-thermometer when constructed in form for a physicians use, and Fig. 2 a longitudinal central section thereof.

A represents the glass tube ordinarily employed in thermometers,provided with a suitable scale upon its face, as shown in Fig. 1. The lower end, a, of this tube is reduced in diameter, and the bulb B is made to encircle this smaller end of the tube, so that the tube shall project down into the bulb and open into it near to the bottom thereof, as shown in Fig. 2.

The concentric space between the wall of the bulb and the lower end of the tube projecting into the same is made large enough to contain the proper charge of mercury, and in filling the bulb and tube, which is done in the customary manner well known to the art,a small portion, 0, of the mercury is separated from the main body of the column in the tube by means of an interposed air space or bubble, D, which, when the thermometer is sealed, isabsolutely confined in the column, so as to separate constantly the small registering-division 0 of mercury from the remainder thereof. This small body 0 of mercury, separated from the rest at the top of the column by the intervening confined air-bubble D, will be carried up when the mercury rises in the tube, but will, by reason of its attraction and frictional adhesion to the sides of the tube, remain at the extreme upper point to which it may be thus carried, when the main column drops again into the bulb, and thus remaining stationary will serve as an accurate register of the extreme height to which the mercury has ascended.

The registering-division 0 may be made to drop back to the bulb, when required,by slight percussion; but the air-bubble D cannot be driven out of the tube, because of the fact that its lower end is constantly immersed in mercury, insuring a continued pressure thereon, even when the column in the tube drops so low as that the air-bubble D is brought to its extreme lower end.

I am aware that manometers have been constructed with a bulb encircling the lower end of anindex-tube, which is open at the top, the bulb being either enlarged and extended (N0 ModeL) J. FISHER.

WEATHER STRIP.

N0. 320,120. Patented June 16, 1885. 

